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n.1.the leakage of gases from the combustion cylinder of an internal combustion engine between the piston and cylinder wall into the crankcase.
References in periodicals archive ?
Blowby is a measure of any inefficiency in a compression cylinder.
Gaps on the gas valves, as with the M16, should always be positioned so they remain separated from each other to prevent excessive gas blowby.
That blowby in the crankcase mixes with oil to make acid and sludge.